Fuse



Oct. 5, 1926. 1,601,726

A. L. EUSTlCE FUSE Filed Feb. 15, 1922 Patented Oct. 5, 1926.

ALFRED L. EUSTICE, OF CHICAGO, ILLINOIS.

FUSE.

Application filed February 15, 1922. Serial No. 536,624.

The present invention relates to fuses. More particularly the presentinvention relates to electric fuses of metal which upon electricaloverload will melt and interrupt the electric circuit in which itisconnected. It has been common practice to provide such fuses withrestricted portions -of greater electrical resistance than the remainderof the fuse whereby said restricted l0 portions will be the parts tofuse in case the capacity of the fuse is exceeded. Certain successfultypes of fuse, as shown for example in my Patent No. 1,217,289, haveinvolved dropout fusible elements or links in which a plurality ofrestricted portions are provided along the length of the fusible elementor link, so that on blowing the fuse a portion of the fusible element orlink between said restricted portions will be separated from the rest ofthe link. As described in my previous patent just referred to. I havefound that, particularly, when the link is enclosed in a casing of theusual type, this dropout action takes place. A decided advantage accruesfrom the fact that only relatively small portions of the fusible memberor link are violatilized and consequently, the pressure in the fusecasing is greatly reduced beyond that occurring in the case of blowing afuse having a link with only one restricted portion. This dropout actionresults, of course, only in connection with fusible elements or linkshaving a plurality of restricted portions. 85 While my invention.described in my prior patent above eferred to, has reduced thevolatilization of metal and consequent pressure very materially fromprior practice I have found that the characteristics of the fusedescribed in my said prior patent can be improved, and one of theobjects of the present invention is to .provide an. improvement over thestructure of my prior patent above referred to with respect to theconformation of the restricted portions of the link. so that thevolatilization of metal and resulting pressure in the fuse casing willbe still further reduced It is a further object of the presentinventionto provide a construction of link which while having theelectrical efficiency and reduction of pressure above referred to, willhave adequate mechanical strength.

A further object of the present invention is to provide a fuse membercomprising an elongated strip of material having restricted portions.said restricted .portions being so designed that without sacrificing anyof the electrical advantages a greater mechanical strength is obtained.

Further objects will appear as the description proceeds.

Referring to the drawings Figure 1 represents a fuse plug containing afuse link embodying the present invention;

Figure 2 is a sectional view taken along the line 22 of Figure 1;

Figure 3 illustrates a flat fuse strip embodying the present invention;

Figure 1 represents. a fuse strip such as illustrated in Figure 3, butbent into a form to fit within the fuse plug illustrated in Figures 1and 2.

Referring first to Figures 1 and 2, a fuse plug is provided having apair of holding members 10 and 11 which may be of insulating materialcapable of being molded, such as hard rubber. Member 10 comprises acylindrical member which may be provided with screw-threads 12 for apurpose which will'be apparent. The member 11 comprises a cap memberadapted to abut one end of the cylindrical member 10. The cap member 11is held in fixed relation with the cylindrical member 10 by means of theshell or casing 13, which may be of relatively thin conducting materialswaged to form screwthreads 1212. The shell 13 also has a turned overend portion 15 for engaging the vided with a hole 20 for the receptionof the v shank 18 of the contact member 16. Said fusible element 19 isbent intermediate of its length inv a plurality of places whereby to fitWithin the chamber formed by the cylindrical member 10. The shank 18 ofthe contact member 16 may be upset after the fusible: element '19 hasbeen mounted thereon, and a rigid connection between said fusibleelement and. said shank 18 may be insuredv by soldering said memberstogether. The contact member 18 will be firmly held within the cap 11between the abutments formed by the head 17 and the end of the fusibleelement 19. Any preferred means may be provided for preventing rotationof the fusible element 19 relative to the cap 11 and undesirablerotation between the cap 11 and the cylindrical member 10.

The manner in which the fusible element 19 may be bent in order to liewithin the chamber provided by the cylindrical member 10 and the cap 11will be clear without detailed explanation from an inspection of Figures2 and 4:. As shown in these figures, the fusible element 19 is bent toprovide a substantially right-angular conformation within thecylindrical member 10 and has an end portion 20 lying outside of thecylindrical member 10, which end portion 20 may lie in a correspondingslot on the outside of said cylindrical member 10. Said end portion 20of the fusible element 19 may have an outer surface engaged by the shellor casing 13. In order to insure a perfect contact between said endmember 20 and shell 13, said members may be soldered together, asindicated by the numeral 21 of Figure 2.

The right hand end of the cylindrical member 10 is provided with theenlargedgrip portion 22, by means of which the fuse plug may be readilymanipulated. Said right hand end of the fuse plug. is provided with asight opening 23 which may have a mica, glass, or other transparentclosure 24:. Said closure 24 may be held in place by any preferredmeans.

It has been found in practice that a fusible element having restrictedportions operates with decided advantages if the number of saidrestricted portions is an odd number. By this arrangement one of therestricted portions lies midway of the others and, as suming substantialuniformity of dimensions of said restricted portions, may be dependedupon to fuse either in case of continued overload or sudden rush ofcurrent such as accompanies a short circuit, whether the otherrestricted portions fuse or not, the latter condition sometimes beingmet with in the event of a gradual overload in distinction to shortcircuit conditions.

In the fuse member illustrated in Figures 3 and 4 three restrictedportions are indicated, the two outer of said restricted portions beingindicated by the numeral 25 and the central restricted portion beingindicated by the numeral 26. Each of the restricted portions has anelongated aperture 27 preferably arranged on the lon 'tudinal centerline of said fuse member. member 19 is notched adjacent to saidelongated aperture 27 as indicated by the numerals 2828, said notchesbeing preferably in the form of a truncated 'V whereby to provideelongated strips 29-29 for carrying current. The aperture 27 shouldpreferably have substantially parallel walls at least as great in lengthas the base of the truncated V and may have rounded ends or ends on anyother preferred contour. The

aid fuse strips 2929 may be designed so that they will fuse when apredetermined load on the fuse member is exceeded. As pointed out above,the central restricted portion 26 will blow either upon extendedoverload or upon heavy rush of current, Whether the other restrictedportions blow or not.

The form of restricted portion disclosed herein provides no distinctline of least mechanical strength along which a bending effect will tendto localize. For this reason the common difficulty of many fuse membersof localizing a bending effect to form an abrupt bend with consequentbreaking is obviated. Though the illustrated construction is preferredat present, it will be clear that other conformations may be employed toaccomplish the result of avoiding the difficulties due to lines of leastresistance to breaking effects.

The description above has been limited more or less to a ty e of fusemember having notches in the orm of a truncated V, which notches havelocated adjacent thereto the elongated slots 27 providing strips ofmaterial of restricted dimensions. There is no intention in this case tolimit the present invention to any such conformation, however, it beingpossible to modify the size and shape of the apertures and the notchesthrough wide limits.

The present invention has been illustrate-i1 in connection with a plugfuse for the reason that this type of fuse requires considerable bendingof the fuse element and therefore presents difficulties in the use offuse elements having restricted portions. It will be understood,however, that the present invention is useful in other types of fuses inwhich mechanical strength is required in combination with accuracy ofthe calibration of the fuse.

One embodiment of the present invention has been described in detail.Many modifications will occur to those skilled in the art. It isintended in this patent to cover all such modifications that fall withinthe scope of the invention as defined by the appended claims.

I claim 1. An enclosed fuse comprising a housing and an elongatedfusible member mounted in said housing, said fusible member having aplurality of restricted portions having an aperture in each of-saidrestricted portions.

2. A fusible member comprising an elongated strip of conducting materialhaving a plurality of restricted portions, each of said restrictedportions being formed with a notch at an edge of said fusible member andhaving an aperture between said notch and the other edge of said fusiblemember.

3. An enclosed fuse comprising a housing, and an elongated fusiblemember within said housing, said fusible member having a plurality ofrestricted portions, each of said restricted portions being providedwith an elongated aperture arranged longitudinally of said member and apair of opposed notches of the shape of atruncated V forming with saidaperture a pair of strips having parallel side walls extendinglongitudinally of said elongated member? 4. An enclosed fuse comprisinga housing and an elongated fusible member located within said housing,said fusible member having a plurality of restricted portions arrangedalong its length, each ofrsaid restricted portions being formed with anotch at an edge of said fusible member andan aperture between saidnotch and the opposite edge of said fusible member.

5. An enclosed fuse comprising a housing and an elongated fusible memberlocated withinsaid housing, said fusible member having a plurality ofrestricted portions arranged along its length, each of said restrictedportions being formed with'a notch at an edge of said fusible member andan aperture between said notch and the opposite edge of said fusiblemember, said notch being wedge-shaped.

6. An enclosed fuse comprising a housing and an elongated fusible memberlocated within said housing said fusible member having a plurality ofrestricted portions arranged along its length, each of said re strictedportions being formed with a notch at an edge of said fusible member andan aperture between said notch and the opposite edge of said fusiblemember, said notch having the form of a truncated V.

7. A fuse comprising a housing,and an elongated fusible'inember bentintermediate its length to fit within said housing, said fusible memberhaving a plurality of re stricted portions, each of said restrictedportions being formed with an elongated aperture arranged along thelongitudinal axis of said member and with a pair of notches, each ofsaid notches having the form of a truncated V, said aperture havingparallel walls at least as long as the bases of said truncatedVs, saidrestricted portions being free from any line of least mechanicalstrength.

8. An enclosed fuse comprising a housing, and an elongated fusiblemember bent intermediate of its length to fit within its housing, saidfusible member having a plurality of restricted portions, each of saidrestricted portions comprising a pair of elongated strips of materialpresenting no line of least mechanical strength.

9. An electrical fusible member comprising an elongated strip of fusiblematerial having a plurality of restricted portions, certain of saidrestricted portions being formed of a notch of wedge-shape and anaperture between said notch and an edge of said strip.

10. An electrical fuse comprising an elongated member having a pluarlityof restricted portions, each of said restricted portions being formedwith a pair of opposed wedge-shaped notches and an elongated aperturebetween said notches providing a pair of parallel strips presenting noline of least mechanical strength.

11. An enclosed fuse comprising a housing, and an elongated fuse memberbent intermediate of its length to fitalong a plurality of sides of-saidhousing, said fuse member having a plurality of restricted portions,said portions being free from a line of least mechanical strength, saidportions being formed with elongated aperture and a wedge-shaped notchadjacent to said aperture.

12. An enclosed fuse comprising a housing, and an elongated fusiblemember mounted in said housing, said fusible member having a pluralityof restricted portions having an elongated aperture in each of saidrestricted portions,

Signed at Chicago, Illinois, this 11th day of February, 1922.

ALFRED L. EUSTICE.

